The present invention relates generally to measuring and detecting apparatus capable of gathering data, and in particular to apparatus for delivering and positioning a sensing probe.
The invention has particular application to the maintenance of a steam generator, particularly a nuclear power plant steam generator.
A typical nuclear steam generator comprises a vertically oriented vessel, a plurality of U-shaped tubes disposed in the vessel so as to form a U-shaped tube bundle, and a tube sheet for supporting the tubes at the ends opposite the U-like curvature, and a dividing plate that cooperates with the tube sheet forming a primary fluid inlet plenum at the one end of the tube bundle and a primary fluid outlet plenum at the other end of the tube bundle. The primary fluid having been heated by circulation through the nuclear reactor core enters the steam generator through the primary fluid inlet plenum. From the primary fluid inlet plenum, the primary fluid flows upwardly through first openings in the U-tubes near the tube sheet which supports the tubes, through the U-tube curvature, downwardly through second openings in the U-tubes near the tube sheet, and into the primary fluid outlet plenum. At the same time, a secondary fluid, known as feedwater, is circulated around the U-tubes in heat transfer relationship therewith thereby transferring heat from the primary fluid in the tubes to the secondary fluid surrounding the tubes causing a portion of the secondary fluid to be converted to steam.
Material deposits tend to settle and accumulate between the tubes on the tube sheet at the bottom, forming a harmful sludge. Sludge profilometry is a method of measuring the heights of such sludge deposits in a nuclear steam generator through the use of a measurement probe, such as an ultrasonic probe, which is delivered between the rows of tubes of the steam generator.
One method of delivering the probe through the rows of tubes is disclosed in U.S. Pat. No. 4,355,536. In accordance with that method, an elongated track, rectangular in transverse cross section, is manually assembled in the steam generator vessel by piecing together track sections for extending the track through a handhole in the vessel wall and along the tube lane between the legs of the U-shaped tube bundle. This necessitates the presence of operating personnel in the steam generator vessel and consequent exposure to harmful radiation. A carriage is mounted for movement along the assembled track, the carriage including means for feeding a flexible probe carrier tape along the length of the track and then deflecting it laterally of the track in between the tube rows.
Operation of this prior profilometry system requires an operator at the handhole of the steam generator vessel to index the carriage along the track, while a second operator monitors and operates remote electronic readout equipment. Constant communication must be maintained between the handhole operator and the remote electronic equipment operator, because they must both operate the equipment in unison. This results in relatively slow run times. The data from the probe are recorded on a strip chart. The strip chart must then be later analyzed, resulting in a time consuming and costly procedure for placing the data in usable form. This off-line data analysis frequently means that the results of the tests are not available until several months after the data are collected.